Transient and long-term effects of Al implantation temperature on electrical and structural properties of 4H-SiC

This study examines the influence of implantation temperature and annealing duration on lattice damage recovery and the electrical properties of Al-implanted 4H-SiC. With the aim of reducing the thermal budget and improving process yield, particular attention is given to implantation at temperatures as low as 350 °C and annealing times below 30 min. Under conventional 30-min annealing, higher implantation temperatures are known to produce Al-implanted layers with lower sheet resistance. This work shows that low implantation temperature is not detrimental for brief annealing treatments: after 10 min at 1800 °C, 350 °C implantation leads to a sheet resistance comparable to the one obtained with 650 °C, and even to a lower value for a 3 min annealing. This can be explained by a cooperative mechanism of atomic rearrangement and Al incorporation in disordered lattice regions. High-resolution X-ray diffraction confirms that the larger structural damage resulting from 350 °C implantation is effectively recovered by brief annealing (e.g. 1800 °C 3 min), producing patterns similar to those resulting from 650 °C implantation and same annealing. Lattice recovery is therefore very rapid. This work shows that the implantation damage favours lattice recovery enhancing dopant activation, but only during the first stage of the annealing. An implantation-induced transient effect in 4H-SiC can be identified highlighting the potential of rapid annealing for efficient dopant activation.